Daisy Martinez recipe. Guajillo chiles (sometimes spelled "huajillo") can be found at either regular grocery stores in the Mexican food section or Mexican food markets. Most of the cook time is passive.
Put the pork in a heavy Dutch oven large enough to fit pork comfortably.
Pour in enough cold water to cover the meat by about 2 inches.
Add 2 tablespoons salt, bay leaf and bring to a boil.
Boil for one hour, skimming foam off surface as necessary.
Cut the stems off the guajillo chiles. Tap out the seeds.
Heat oil in a medium skillet over medium heat.
Add half the chiles and toast them in the skillet, turning with tongs, until they crisp up a bit and change color, about 4 minutes.
Lift out chiles and repeat with remaining chiles.
Pour enough boiling water over the toasted chiles to cover them. Soak until completely softened, about 20 minutes. Drain well.
Wipe out the skillet with paper towels, put the onion and tomatoes cut sides down in the skillet. Cook, turning the veggies as often as necessary, until tomatoes are blackened on all sides and the onions are blackened on both flat sides.
After the pork cooks one hour, ladle off 2 cups of the cooking liquid and pour into blender. Add onions and puree until smooth. Add chiles and tomatoes and blend until smooth.
Ladle off another 2 cups of the cooking liquid and set aside. Drain pork, discard remaining liquid, wipe out the pot.
Set the pot over medium-low heat and add the oil or lard. Stir in the flour and cook, stirring, 3-4 minutes.
Pour the chili sauce into the pot slowly, stir well.
Return the pork to a simmer, cover the pot and cook until tender, about 1 hour. While it cooks, there should be enough sauce to moisten the pork. If not, add reserved pork cooking liquid as needed.
Serve hot over white rice or with flour tortillas.